Proximity sensing systems and methods

ABSTRACT

Methods, systems and device are provided for improving the range and accuracy of proximity measurement such as in ultrasonic sensing systems. In particular, the blind zone caused by reverberation signals can be reduced or eliminated by attenuating signals received during the time period corresponding to the blind zone without. In an implementation, an attenuator circuit is selected by a switch to process received signals during the blind zone time period and deselected by the switch after the time zone time period. Additionally, the accuracy and range of the measurement can be improved by varying the gain provided to the received signals based on the varying measuring distance. In an implementation, a gain-adjustable amplifier is controlled by a gain control signal to provide incremental gain as time increases.

CROSS-REFERENCE

This application is a continuation application of U.S. Ser. No.14/463,578, filed on Aug. 19, 2014, which is a continuation applicationof International Application No. PCT/CN2014/075192, filed on Apr. 11,2014, the content of which is hereby incorporated by reference in theirentirety.

BACKGROUND OF THE INVENTION

Proximity sensors such as ultrasonic sensors have been widely used todetect distance to objects. In particular, ultrasonic sensors aretypically configured to generate ultrasonic signals with an ultrasonictransducer and to receive the echo signals reflected back by theobjects. By calculating the time interval between sending the ultrasonicsignal and receiving the echo signal, the distance to an object can bedetermined based on the propagation speed of sound through thepropagation medium such as air.

Traditionally, the application of the ultrasonic sensors is limited bythe existence of the blind zone, which is caused by residual mechanicalvibration of the ultrasonic transducer. Ultrasonic transducers aretypically configured to generate ultrasonic signals by high frequencyvibrations or resonance caused by an excitation signal. For example, apulse of electrical energy can cause a piezoelectric transducer tovibrate at a given frequency due to piezoelectricity, thereby generatingan ultrasonic sound wave. The echo of the transmitted ultrasonic signalas reflected by an object can then be detected and evaluated todetermine a distance to the object. However, once the excitation signal(e.g., electrical signal) is removed, the vibration of the transducerusually does not stop immediately. Rather, due to elasticity, thetransducer typically continues to vibrate for a period of time, albeitin a dampening fashion. Such residual vibration or reverberation can bedetected by the ultrasonic sensor. Reverberation signals can obscure thedetection of echo signals. The blind zone is the area surrounding theultrasonic transducer in which echo signals cannot be reliably detectedas distinguished from reverberation signals.

Existing methods attempt to solve the problem of blind zone using eithera software approach or a mechanical approach. Under the softwareapproach, the detection of ultrasonic signals is disabled during thetime period corresponding to the blind zone so as to avoid detecting thereverberation signals as echo signals. However, the software approachmerely avoids but does not reduce or remove the blind zone. That is,objects located within the blind zone still cannot be reliably detected.Using a mechanical approach, the receiver probe of the ultrasonic sensorcan be padded or otherwise protected using physical barriers. While thisapproach can reduce or remove the blind zone by reducing the amplitudeof the reverberation signals reaching the receiver probe, the complexityand cost of manufacturing is likely to increase.

SUMMARY OF THE INVENTION

The present invention provides methods and systems for reducing or eveneliminating the blind zone, thereby decreasing the minimum measuringdistance, without increasing the production cost. Unlike the softwareapproach mentioned above, the present invention makes it possible todetect objects located within the blind zone, effectively reduced oreliminating the blind zone. Additionally, the present invention isimplemented at the circuit level, thereby avoiding the added cost ofproduction associated with the mechanical approach mentioned above.

According to an aspect of the present invention, an ultrasonic sensingsystem is provided. The ultrasonic sensing system comprises anultrasonic transmitter configured to provide a transmission ofultrasonic signals; an ultrasonic receiver configured to receiveultrasonic signals generated as a result of the transmission includingreverberation signals and echo signals; an attenuator circuitconnectable to the ultrasonic receiver via a switch, the attenuatorcircuit operable for attenuating the received ultrasonic signals; and amicrocontroller unit (MCU) configured to control the switch toelectrically couple the ultrasonic receiver with the attenuator circuitonly during a predetermined period of time after the transmission ofultrasonic signals.

In some embodiments, the ultrasonic transmitter is the ultrasonicreceiver. The predetermined period of time can corresponds to a timeperiod during which the reverberation signals are detectable. Thepredetermined period of time can correspond to a blind zone time period.

In some embodiments, the attenuator circuit is selected based at leastin part on a previously-measured amplitude of a reverberation signal oran echo signal.

In some embodiments, the switch includes a single-pole double-throw(SPDT) switch.

In some embodiments, the ultrasonic sensing system described hereinfurther comprises a booster configured to increase an energy levelassociated with the transmission of the ultrasonic signal. The boostercan be configured to improve the power level of an electric signal thatis usable for causing the transmission of ultrasonic signals.

In some embodiments, the ultrasonic sensing system described hereinfurther comprises a gain-adjustable amplifier configured to amplify theecho signals.

In some embodiments, the MCU is further configured to control thegain-adjustable amplifier to vary its gain based at least in part on avalue of a timer that corresponds to a measuring distance from theultrasonic sensing system. The MCU may control the gain-adjustableamplifier based on previously-measured data.

In some embodiments, the MCU is further configured to control the switchto electrically couple the ultrasonic receiver with the gain-adjustableamplifier without electrically coupling the attenuator circuit with thegain-adjustable amplifier after the predetermined period of time haselapsed.

In some embodiments, the ultrasonic sensing system described hereinfurther comprises a comparator connected to the gain-adjustableamplifier that is configured to compare an output of the gain-adjustableamplifier with a predetermined threshold value. The MCU is furtherconfigured to control a gain of the gain-adjustable amplifier based atleast in part on an output of the comparator. The comparator may or maynot be integrated with the MCU.

In some embodiments, the ultrasonic sensing system described hereinfurther comprises an analog-to-digital converter (ADC) connected to thegain-adjustable amplifier that is configured to convert the output ofthe gain-adjustable amplifier to a digital value. The gain-adjustableamplifier can be controlled based at least in part on an output of theADC. The ADC may or may not be integrated with the MCU. In someembodiments, the comparator and the ADC are used in conjunction todetermine an occurrence of a peak amplitude.

According to another aspect of the present invention, a method forultrasonic sensing is provided. The method can comprise detecting asignal after termination of a transmission of ultrasonic signals, thedetected signal can be an echo signal or a reverberation signal;determining whether the detection of the ultrasonic signal occurs withina predetermined period of time from the terminal of the transmission ofultrasonic signals; in response to a determination that the detection ofthe signal occurs within the predetermined period of time, attenuatingthe detected signal to sufficiently reduce interference caused byreverberation from the transmission of the ultrasonic signals; and inresponse to a determination that the detection of the signal occursafter the predetermined period of time has elapsed, processing, withoutattenuating, the detected signal to determine proximity of an object.

In some embodiments, the predetermined period of time corresponds to atime period during which the reverberation is detectable. In someembodiments, the predetermined period of time corresponds to a blindzone time period.

In some embodiments, the ultrasonic signals transmitted by thetransmission are amplified prior to the transmission of the ultrasonicsignals, for example, using a booster.

In some embodiments, attenuating the detected ultrasonic signal is basedat least in part on amplitude of one or more previously-measured signal.The previously-measured signals can include a reverberation signal, anecho signal, or both.

In some embodiments, processing the detected ultrasonic signal includesdetermining occurrence of a peak amplitude using a comparator and ananalog-to-digital converter (ADC). Zero, one, or both of the comparatorand the ADC can be included in a multi-controller unit (MCU).

The method described herein can further comprise providing a gain to thedetected ultrasonic signal based at least in part on previously-measureddata. The previously-measured data can correlate a measuring distanceand a gain suitable for the measuring distance.

The method described herein can further comprise providing a gain to thedetected ultrasonic signal based at least in part on a timer value.

According to another aspect of the present invention, an ultrasonicsensing system is provided. The system can comprise an ultrasonictransmitter configured to provide a transmission of ultrasonic signals;an ultrasonic receiver configured to receive ultrasonic signalsgenerated as a result of the transmission including reverberationsignals and echo signals; and an attenuator circuit connectable to theultrasonic receiver, the attenuator circuit operable for eliminatingsubstantially all of the reverberation signals without eliminating theecho signals. In some embodiments, the ultrasonic transmitter is theultrasonic receiver.

The attenuator circuit can be connected to the ultrasonic receiver onlyduring a predetermined period of time. The predetermined period of timecorresponds to a blind zone time period. The attenuator circuit can beselected based at least in part on a previously-measured amplitude of asignal such a reverberation signal or an echo signal.

In some embodiments, the ultrasonic sensing system described hereinfurther comprises a booster configured to increase an energy levelassociated with the transmission of the ultrasonic signal. The boostercan be configured to increase a voltage level of an electric signal thatis usable for causing the transmission of ultrasonic signals.

In some embodiments, the ultrasonic sensing system described hereinfurther comprises a microcontroller unit (MCU) configured to control aswitch to electrically couple the ultrasonic receiver with theattenuator circuit only during a predetermined period of time after thetransmission of ultrasound signals. The switch can include a single-poledouble-throw (SPDT) switch.

In some embodiments, the ultrasonic sensing system described hereinfurther comprises a gain-adjustable amplifier connectable to theultrasonic receiver via the switch and connected to the attenuatorcircuit in series, the gain-adjustable amplifier configured to amplifythe echo signals.

In some embodiments, the MCU is further configured to control thegain-adjustable amplifier to vary its gain based at least in part on avalue of a timer that corresponds to a measuring distance from theultrasonic sensing system. The MCU may control the gain-adjustableamplifier based on previously-measured data.

In some embodiments, the MCU is further configured to control the switchto electrically couple the ultrasonic receiver with the gain-adjustableamplifier without electrically coupling the attenuator circuit with thegain-adjustable amplifier after the predetermined period of time haselapsed.

In some embodiments, the ultrasonic sensing system described hereinfurther comprises a comparator connected to the gain-adjustableamplifier that is configured to compare an output of the gain-adjustableamplifier with a predetermined threshold value. The MCU can be furtherconfigured to control a gain of the gain-adjustable amplifier based atleast in part on an output of the comparator. The comparator may or maynot be integrated with the MCU.

In some embodiments, the ultrasonic sensing system described hereinfurther comprises an analog-to-digital converter (ADC) connected to thegain-adjustable amplifier that is configured to convert the output ofthe gain-adjustable amplifier to a digital value. The gain-adjustableamplifier can be controlled based at least in part on an output of theADC. The ADC may or may not be integrated with the MCU. In someembodiments, the comparator and the ADC are used in conjunction todetermine an occurrence of a peak amplitude.

According to another aspect of the present invention, a method forultrasonic sensing is provided. The method comprises detecting anultrasonic signal after termination of a transmission of ultrasonicsignals, wherein the detected ultrasonic signal is an echo signal or areverberation signal; and attenuating the detected ultrasonic signal,thereby substantially eliminating the reverberation signal withouteliminating the echo signal. In some embodiments, the attenuation of thedetected ultrasonic signal is applied only within a predetermined periodof time from the transmission of the ultrasonic signals. Thepredetermined period of time can correspond to a blind zone time period.

In some embodiments, the ultrasonic signals transmitted by thetransmission are amplified prior to the transmission of the ultrasonicsignals, for example, by a booster.

In some embodiments, attenuating the detected ultrasonic signal is basedat least in part on a previously-measured amplitude of a reverberationsignal or an echo signal.

In some embodiments, the method described herein further comprisesdetermining occurrence of a peak amplitude using a comparator and ananalog-to-digital converter (ADC). Zero, one or both of the comparatorand the ADC can be included in a multi-controller unit (MCU).

In some embodiments, the method described herein further comprisesproviding a gain to the detected ultrasonic signal based at least inpart on previously-measured data. The previously-measured data cancorrelate a measuring distance and a gain suitable for the measuringdistance.

In some embodiments, the method described herein further comprisesproviding a gain to the detected ultrasonic signal based at least inpart on a timer value.

According to another aspect of the present invention, a method forultrasonic sensing is provided. The method comprises adjusting anamplifier to provide a first gain to received ultrasonic signals basedat least in part on previously-measured adjustable gain control (AGC)data; and adjusting the amplifier, at a later point in time, to providea second gain that is greater than the first gain based at least in parton the previously-measured AGC data. The previously-measured AGC datacan correlate a measuring distance and a gain suitable for the measuringdistance. For instance, the gain can increase, at least in part, as themeasuring distance increases.

In some embodiments, the method described herein further comprisesadjusting the amplifier to provide increasing gains, over time, until anecho signal is detected or until a predetermined measurement time isreached.

In some embodiments, the received ultrasonic signals are attenuated,prior to being amplified, only if the ultrasonic signals are receivedduring a predetermined period of time. During the predetermined periodof time, the received ultrasonic signals can be attenuated so as toeliminate substantially all of reverberation signals without eliminatingecho signals.

In some embodiments, the received ultrasonic signals are attenuatedbased at least in part on a previously-measured amplitude of areverberation signal or an echo signal. The predetermined period of timecan include a blind zone time period.

In some embodiments, the method described herein further comprisesdetermining occurrence of a peak amplitude using a comparator and ananalog-to-digital converter (ADC). Zero, one or both of the comparatorand the ADC can be included in a multi-controller unit (MCU).

It shall be understood that different aspects of the invention can beappreciated individually, collectively, or in combination with eachother. Various aspects of the invention described herein may be appliedto any of the particular applications set forth below. Other objects andfeatures of the present invention will become apparent by a review ofthe specification, claims, and appended figures.

INCORPORATION BY REFERENCE

All publications, patents, and patent applications mentioned in thisspecification are herein incorporated by reference to the same extent asif each individual publication, patent, or patent application wasspecifically and individually indicated to be incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings of which:

FIG. 1 illustrates an exemplary ultrasonic sensor, in accordance with anembodiment.

FIG. 2 illustrates exemplary signals detected by an ultrasonic receiveras a result of an ultrasonic transmission, in accordance with someembodiments.

FIG. 3 illustrates an exemplary process for implementing blind zonereduction or removal, in accordance with an embodiment.

FIG. 4 illustrates an exemplary circuit diagram of an ultrasonic sensingsystem, according to an embodiment.

FIG. 5 illustrates some exemplary AGC gain values (AGC values)corresponding to varying measuring distances, in accordance with anembodiment.

FIG. 6 illustrates an exemplary process for implementing the time-basedgain control as described herein, in accordance with an embodiment.

FIG. 7 illustrates an exemplary process for determining the occurrenceof peak amplitude, in accordance with an embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Methods, systems and device are provided for reducing or eliminating ablind zone associated with ultrasonic sensors, thereby decreasing theminimum measuring distance, without reducing the maximum measuringdistance and without increasing production cost. According to an aspectof the present invention, methods and systems for reducing oreliminating blind zone associated with ultrasonic sensing are provided.In some embodiments, an attenuator circuit is introduced to attenuatethe received signals during the time period corresponding to the blindzone in order to remove substantially all reverberation signals whilepreserving substantially all echo signals as reflected from objects. Theselection and de-selection of the attenuator circuit may be achieved bya controllable switch. The amount of attenuation provided by theattenuator circuit may be configurable based on values (e.g., amplitude)of actually measured reverberation signals and echo signals, among otherfactors.

According to another aspect of the present invention, methods andsystems are provided for dynamically adjusting gains of echo signals toimprove the accuracy of proximity measurement. Specifically, again-adjustable amplifier may be provided to amplify received signalsbased on a current measuring distance as indicated by the time that haselapsed since the start of the measurement. The amount of gain of thegain-adjustable amplifier may be controlled by a controller based on themeasuring distance. The longer the measurement distance, the moreattenuated the echo signals tend to be, and hence the more gain isprovided by the gain-adjustable amplifier to amplify the echo signals.In some embodiments, amount of gain is adjusted periodically by thecontroller based on empirical measurement data.

According to another aspect of the present invention, methods andsystems are provided for using the analog-to-digital converter (ADC) inconjunction with a comparator to improve the precision and accuracy ofproximity measurement. In particular, the comparator can be used totrigger proximity measurement and the ADC can be used to determine,within a predetermined period of time, a point in time when the relativepeak amplitude is received. This point in time can then be used in thecalculation of the distance to the object from which the echo signal isreflected. By pinpointing the time of the peak amplitude, the precisionand accuracy of the proximity measurement is improved.

According to an aspect of the present invention, methods and systems areprovided for increasing the power associated with the ultrasonictransmission. Boosting of the transmission power is preferable, forexample, to overcome the attenuation of the sound signals in thesurrounding environment and/or to increase the upper limit of themeasurement range. To increase the transmission power, the transmissioncircuit of the ultrasonic system can include a booster that isconfigured to increase the electrical power used for the transmission.In an embodiment, the booster can be implemented by a transformer (e.g.,a step-up transformer) configured to increase the voltage level of theelectrical signal provided by the controller.

It shall be understood that different aspects of the invention can beappreciated individually, collectively, or in combination with eachother. Various aspects of the invention described herein may be appliedto any of the particular applications set forth below. Other objects andfeatures of the present invention will become apparent by a review ofthe specification, claims, and appended figures.

FIG. 1 illustrates an exemplary ultrasonic sensor 100, in accordancewith an embodiment. The ultrasonic sensor 100 includes a transmitter 102and a receiver 104. The ultrasonic transmitter is configured to convertelectrical signals to sound signals whereas the ultrasonic receiver isconfigured to convert sound signals to electrical signals. In somecases, the ultrasonic receiver and the ultrasonic transmitter areimplemented as separate devices. In other cases, the ultrasonic receiverand the ultrasonic transmitter are implemented by the same devicecapable of both transmitting and receiving ultrasonic signals. As usedherein, the term ultrasonic transducer can refer to an ultrasonictransmitter, ultrasonic receiver, or both. The arrow from the ultrasonictransmitter 102 to the ultrasonic receiver 104 illustrates areverberation 106 that can reach the ultrasonic receiver, e.g., afterthe transmitter 102 stops actively transmitting ultrasonic signals.

In some embodiments, the ultrasonic transducer (e.g., ultrasonictransmitter, ultrasonic receiver or both) can be constructed usingpiezoelectric principles. For example, the ultrasonic transducer caninclude a piezoelectric transducer made of natural or syntheticmaterials that exhibit piezoelectricity such as certain crystals (e.g.,quartz, berlinite, sucrose, rochelle salt, topaz, or tourmaline-groupminerals), bones, biological materials (e.g., tendon, silk, wood,enamel, dentin, or DNA), synthetic crystals (e.g., galliumorthophosphate or langasite), synthetic ceramics (e.g., lead zirconatetitanate, barium titanate, lead titanate, potassium niobate, lithiumniobate, lithium tantalate, sodium tungstate, or zinc oxide), polymers(e.g., polyvinylidene fluoride), organic nanostructures, and the like.

Alternatively, the ultrasonic transducer can be constructed usingnon-piezoelectric principles. For example, the ultrasonic transducer cancomprise magnetostrictive materials that changes size when exposed tomagnetic fields. As another example, the ultrasonic transducer caninclude a capacitor microphone that uses a thin plate which moves inresponse to ultrasound waves, causing changes in the electric fieldsaround the plate to convert sound signals to electric currents.

FIG. 1 also illustrates some exemplary hardware pins provided by anexemplary ultrasonic proximity sensor board. In various embodiments, thedefinition of the hardware pins can be defined according to the specificrequirement of actual applications. More, less and/or different hardwarepins may be provided in various embodiments. In an illustrativeembodiment, the hardware pins are defined as follows:

Vcc—power supply (the voltage is defined by actual demands);

Trig/Tx—external logic trigger to launch a measurement/UART (UniversalAsynchronous Receiver/Transmitter) terminal used to transmit measurementresults or response to external commands;

Echo/Rx—measurement result shown as the pulse width/UART receivingterminal used to receive commands;

GND—reference ground to power and signals.

FIG. 2 illustrates exemplary signals detected by an ultrasonic receiveras a result of an ultrasonic transmission, in accordance with someembodiments. As illustrated, an excitation electrical signal or drivingpulse 202 causes an ultrasonic transmitter to vibrate and transmitultrasonic signals. The driving pulse 202 is removed at around time t₁.However, the transmitter does not immediately stop vibrating even thoughthe driving pulse 202 is removed (i.e., voltage level is zero). Instead,the transmitter continues to ring down or residually vibrate, causingresidual vibration signal or reverberation signal 214 that can bereceived by the ultrasonic receiver. The signal level as received by thereceiver probe is represented by 210. The reverberation can last for aperiod of time t_(b)=t₂−t_(1,) during which reverberation signals, ifnot suppressed (e.g., amplitude of the signal artificially attenuated),can obscure the receipt of true echo signals. The time period t_(b) isthus referred to as the blind zone time period or dead zone time period,indicating a period of time when echo signals cannot be reliabledetected as distinctly from the reverberation signals. During the blindzone time period, reverberation signals are not suppressed, may bestrong enough (e.g., with sufficient amplitude) to trigger the thresholdor triggering level 208 of a comparator. Such comparator triggeringthreshold is often used to determine whether true echo signals have beenreceived.

Based on the velocity of sound c, a blind distance d_(b) from thetransducer can be calculated as d_(b)=½*c*t_(b), within which an objectcannot be reliably detected because the echo from the object can beobscured by reverberation signals. In other words, for an object in theblind zone, the time for the ultrasonic signal to reach the object andtravel back to the transducer is less or equal than t_(b). A blind zonerefers to an area surrounding the transducer that is covered by thetransmission (i.e., a blind zone) within which objects cannot bereliably detected because echoes from the objects tend to be obscured bythe presence of reverberation. As used herein, the term blind zone timeperiod is used to refer to t_(b), during the ring down of the transducerprevents or obscures the detection of true echo signals. In variousembodiments, the shape or size of the blind zone may be determined bythe propagation medium, material and/or disposition of the transducer,characteristics of the excitation signal, and other factors. In general,reducing or eliminating blind zone is desirable for increasing thedetectable range of proximity sensors, especially for close-rangedetection.

FIG. 2 illustrates the receiver signal in two exemplary situations. Inthe first scenario 204, an object is located beyond the blind zone ofthe transducer. Thus, the echo signal 216 occurs after the blind zonetime period, after the occurrence of the reverberation signal 214. Asillustrated, when the object is located beyond the blind zone, the echosignal from the object is not obscured by the reverberation signal.

In the second scenario 204, an object is located within the blind zoneof the transducer. As a result, the echo signal 216 occurs during thesame blind zone time period as the reverberation signal 214. In theillustrated scenario, it is clear that, if not suppressed, thereverberation signal 214 can obscure or prevent the detection of thetrue echo signal 216.

In both illustrated cases, the reverberation signal 214 is shown asbeing suppressed or otherwise attenuated (e.g., by a hardware attenuatorcircuit) to be lower than the triggering value 208 such that thereverberation signal does not falsely trigger the comparator. Asexplained in further detail, such attenuation of the received signalsduring the blind zone time can be used to effectively reduce or removethe impact of blind zone.

Using the attenuation techniques of the present invention, the true echosignal can also be attenuated if it occurs during the blind zone timeperiod. However, the echo signals are typically stronger than thereverberation signals, especially within close range. Therefore it ispossible to attenuate the reverberation signals so as to remove it(e.g., reducing the amplitude to be less than the triggering value ofthe comparator) while preserving the true echo signal (e.g., leaving theamplitude still greater than triggering value of the comparator). Thereverberation is typically already weakened by the time it reaches thereceiver probe. Other factors contributing to the reduced power of thereverberation signals can include the distance between the receiver andthe transmitter, the launch angle of the transmitter and/or otherfactors. For example, the launch angle of the ultrasonic transmittertypically cannot reach 180 degrees. Exemplary launch angles can includebut not limited to 30, 60, 90, 120, and 150 degrees. In contrast, theecho as reflected by objects located close to the receiver (i.e., in theblind zone) is typically not much weakened and typically enters directlyinto the receiver at a very small angle, preserving most power of thesignal. Based on these factors, echo signals are typically stronger thanthe reverberation signals detected within the blind zone time period.Therefore, it is possible to remove substantially all the reverberationsignals while preserving most of the echo signals within the blind zonetime period by adjusting the amount of the attenuation. As shown in thescenario 206, even if attenuated by the attenuator circuit connected tothe receiver, the reverberation signal 214 can be substantially orentirely removed (e.g., amplitude of the attenuated reverberation signal214 is less than the triggering value 208) while substantiallypreserving the true echo signal 216 (e.g., amplitude of the attenuatedecho signal is still greater than the triggering value 208).

According to an aspect of the present invention, methods and systems forreducing or eliminating blind zone in proximity sensing systems areprovided. FIG. 3 illustrates an exemplary process 300 for implementingblind zone reduction, in accordance with an embodiment. Some or allaspects of the process 300 (or any other processes described herein, orvariations and/or combinations thereof) may be performed under thecontrol of one or more computers, processors, or control systemsconfigured with executable instructions and may be implemented as code(e.g., executable instructions, one or more computer programs or one ormore applications) executing collectively on one or more processors, byhardware or combinations thereof. The code may be stored on acomputer-readable storage medium, for example, in the form of a computerprogram comprising a plurality of instructions executable by one or moreprocessors. The computer-readable storage medium may be non-transitory.The order in which the operations are described is not intended to beconstrued as a limitation, and any number of the described operationsmay be combined in any order and/or in parallel to implement theprocesses. For example, aspects of the process 300 can be implemented bycomponents of an ultrasonic sensor system such as illustrated in FIG. 4.

In an embodiment, the process 300 includes detecting 302 a signal afterthe termination of a transmission of ultrasonic signals. Thetransmission of the ultrasonic signals can occur in a manner describedin FIGS. 1-2. For example, a pulse of electrical energy can be appliedto a piezoelectric transmitter, causing it to vibrate or resonate,thereby generating sound waves. When the electrical energy is removedfrom the transmitter, the transmission is considered terminated.However, as discussed above, the vibration or resonance of thetransmitter does not stop immediately. Rather, the transmitter willcontinue to vibrate, although at dampening amplitudes, for a period oftime. Such reverberation can be detected by a receiver and converted toan electrical signal (i.e., a reverberation signal). If the transmittedultrasonic signal is also reflected by an object, the echo may bedetected by the receiver and converted to an electrical signal (i.e., anecho signal). From the perspective of the receiver, the detectedelectrical signal can be either an echo signal or a reverberationsignal.

The process 300 further comprises determining 304 whether the detectedsignal is detected within a blind zone time period associated with anultrasonic sensor, such as discussed in FIG. 2. For example, it can bedetermined whether the detection of the signal occurs within apredetermined period of time from the terminal of the transmission ofultrasonic signals. The predetermined period of time can be the timeinterval t_(b) discussed above in FIG. 2 that corresponds to the blindzone time period. In an implementation, a timer associated with anultrasonic sensor is started when the transmission of ultrasonic signalsterminates or when the transmission starts. The current timer value canbe compared with a predetermined blind zone time period (e.g., t_(b)) todetermine whether the signal was detected with the blind zone timeperiod.

If the signal is detected within the blind zone time period, thedetected signal is attenuated 306 so as to reduce the power (e.g.,amplitude) of the signal. The detected signal may be an echo signal orreverberation signal that is attenuated during the blind zone timeperiod. However, within close range, echo (and the detected echo signal)tends to be stronger than reverberation (and the detected reverberationsignal). This is because the reverberation is typically already weakenedby the time it reaches the receiver probe. Other factors contributing tothe reduced power of the reverberation signals can include the distancebetween the receiver and the transmitter, the launch angle of thetransmitter and/or other factors. For example, the launch angle of theultrasonic transmitter typically cannot reach 180 degrees. Exemplarylaunch angles can include but not limited to 30, 60, 90, 120, and 150degrees. In contrast, the echo as reflected by objects located close tothe receiver (i.e., in the blind zone) is typically not much weakenedand typically enters directly into the receiver at a very small angle,preserving most power of the signal. Based on these factors, echosignals are typically stronger than the reverberation signals detectedwithin the blind zone time period. Therefore, it is possible to removesubstantially all the reverberation signals while preserving most of theecho signals within the blind zone time period by adjusting the amountof the attenuation.

In an embodiment, the amount of attenuation is selected based on theamplitude of actually measured reverberation signals and/or echosignals. For example, if the maximum amplitude (or other suitable value)based on actually measured reverberation signals is V_(r) and theminimum threshold voltage to trigger proximity measurement is V₀,(hereinafter the triggering value), then the amount of attenuation maybe set to V_(r)−V₀ or greater to ensure that the amplitude of anyvibration residual signal is reduced to be at or below the triggeringV₀. On the other hand, to ensure that the echo signals, even afterattenuation, is still strong enough to trigger proximity measurement,the attenuation amount can be set to be less than V_(e)−V₀, where V_(e)is minimum amplitude (or other suitable value) based on actuallymeasured echo signals. Thus, the amount of attenuation, ΔV can beselected as follows:

V _(r) −V ₀ <ΔV<V _(e) −V ₀

In an alternative embodiment, the amount of attenuation can be selectedto be greater than the difference between the received reverberationsignal V_(r) and the triggering value V₀, but not less than thedifference between the received echo signal and the triggering value.However, the amount of attenuation still needs to be less than theminimum echo signal to preserve the echo signals. In other words,

ΔV>V _(r) −V ₀;

ΔV≧V _(e) −V ₀; and

ΔV<V_(e)

In another alternative embodiment, the amount of attenuation ΔV can beset to be greater than a measured reverberation signal such thatV_(r)<ΔV<V_(e). In various embodiments, Vr, Ve, and/or V0 values aredetermined based on test or calibration measurements. For example, anyof the above values may be an average, mean, maximum, minimum, or anyother derivation of the measured values.

In some embodiments, after the attenuation is applied, the reverberationsignals are reduced to zero while the echo signals can be reduced tonon-zero values below the triggering value. In such an embodiment,post-attenuation amplification may be necessary to bring the attenuatedecho signals above the triggering value in order to trigger proximitymeasurement processing. Amplification can also be necessary to detectecho signals received outside the blind zone time period to compensatefor the attenuation caused by the propagation medium. In general, thefurther away an object is from the ultrasonic receiver, the moreattenuated the echo signal as reflected by the object is. To compensatefor the greater attenuation of the echo signals, greater amplificationor gain can be applied as the measurement range increases. Methods forproviding dynamically adjusted gain control are discussed in furtherdetail elsewhere in the disclosure.

Still referring to FIG. 3, if the detected signal is determined to bedetected outside the blind zone time period (e.g., the timer value isgreater than the blind zone time period), then attenuation of thedetected signal is not needed (i.e., skipping block 306) because theresidual signals are considered to have dampened below the minimumtriggering value by then and the detected signal is presumably an echosignal. In some embodiments, the attenuation is switched on and offaccording to the value of a timer, which may be started at the start orend of the ultrasonic transmission. When the value of the timer iswithin the blind zone time period, the attenuation is switched on toattenuate the received signals. When the value of the timer has exceedsthe blind zone time period, the attenuation is switched off so that thereceived signals are no longer attenuated. In an alternative embodiment,the attenuator may be configured to provide different degrees ofattenuation during or beyond the blind zone time period. For example,greater attenuation may be provided during the blind zone time periodthan outside the blind zone time period.

Regardless of whether the signal is attenuated, the process 300 caninclude further processing 308 the signal. In some embodiments,processing 308 the signal can include amplifying the signal whether itis attenuated or not. As discussed above, such amplification may benecessary to increase the power of echo signals to a level that issufficient to trigger the proximity measurement processing. In someembodiments, processing 308 the signal can include calculating the timebetween the sending of an ultrasonic signal and receiving the echo,thereby measuring the distance to an object. As described in furtherdetail below, methods are provided for improving the precision andaccuracy of the proximity measurement.

FIG. 4 illustrates an exemplary circuit diagram of an ultrasonic sensingsystem 400, according to an embodiment. In some embodiments, theultrasonic sensing system 400 may include more or less components thanthose shown in FIG. 4. The ultrasonic sensing system 400 can beconfigured to implement aspects of the techniques discussed herein. Forexample, the ultrasonic sensing system can be configured to increase themeasurement range of the ultrasonic sensing system by reducing oreliminating the blind zone, for example, by applying the time-basedattenuation of received signals as discussed in FIG. 3. Additionally,the ultrasonic sensing system 400 can be configured to maintain or evenincrease the upper limit of the measurement range of the ultrasonicsensing system by increasing the energy of the ultrasonic transmissionand/or by amplifying the received signals. Finally, the ultrasonicsensing system 400 can be configured to provide improved reliability andaccuracy of proximity measurement by providing dynamic gain control ofthe received signals and by using an analog-to-digital converter (ADC)to determine the occurrence of peak amplitude.

The ultrasonic sensing system 400 comprises an ultrasonic transmitter402 and an ultrasonic receiver 404. The ultrasonic transmitter 402 isconnected to a transmitter circuit and the ultrasonic receiver 404 isconnected to a receiver circuit. Either or both of the transmittercircuit and receiver circuit can be controlled at least in part by acontroller 412. The ultrasonic transmitter 402 is configured to transmitultrasonic signals in response to electrical signals and the ultrasonicreceiver 404 is configured to convert received sound signals intoelectrical signals. For example, the ultrasonic transmitter 402 and/oran ultrasonic receiver 404 can be implemented by a piezoelectrictransducer discussed in connection with FIG. 1. While the ultrasonictransmitter 402 and the ultrasonic receiver 404 are illustrated asseparate devices, in some embodiments, they can be implemented by asingle device such as one single piezoelectric transducer.

According to an aspect of the present invention, methods and systems areprovided for increasing the power associated with the ultrasonictransmission. In some circumstances, boosting of the transmission poweris preferable, for example, to overcome the attenuation of the soundsignals in the surrounding environment and/or to increase the upperlimit of the measurement range. For example, sound waves can be absorbedby wave-absorbing materials such as carpet, sponge, and the like.Therefore, when measuring proximity in a carpeted room, the ultrasonictransmission power may need to be increased to compensate for suchattenuation. Additionally, the more power the transmitted sound has, themore likely that the sound will reach a far away object and the echowill travel back at a detectable level. Therefore, increasing the powerof the transmission can increase the upper limit of the measurementrange of an ultrasonic sensing system.

To increase the transmission power, ultrasonic transmitter 402 can beconnected to a booster circuit 422 (hereinafter booster) that isconfigured to increase the electrical power used for the transmission.In an embodiment, the booster 422 can be implemented by a transformer(e.g., a step-up transformer) configured to increase the voltage levelof the electrical signal provided by the controller. Traditionalinverter circuit typically can supply only as much as twice the workingvoltage to drive the ultrasonic transmitter. Such limited power increasein the transmitted ultrasonic waves may be insufficient to account forthe attenuating effect caused wave-absorbing material such as sponge,carpet, and the like in the surrounding environment. In contrast, abooster circuit can boost the transmission voltage by much as six times(or even higher, depends on the hardware design) as the operatingvoltage. With the significantly improved transmitting power, thereflected wave can be more easily received and used to trigger thereceiving circuit even with wave-absorbing materials in the surroundingenvironment.

Preferably, the booster 422 is configured to increase the voltage levelof the electrical signal such that the increased voltage level stayswithin the voltage range associated with the ultrasonic receiver 404.Furthermore, additional mechanisms may be required (e.g., when thedriving current from the controller 412 is not sufficient) andimplemented as part of the transmitter circuit to increase the outputcurrent and to maximize the power of the transmission.

According to another aspect of the present invention, the ultrasonicsensing system 400 provides methods for reducing the impact of blindzone or to realize zero-blind zone (e.g., reducing the size of the blindzone to zero). The methods can be similar to that discussed inconnection with FIG. 3. As discussed above, reverberation can cause thegeneration of reverberation signals that can be mistaken for echosignals during the blind zone time period. The present inventionaddresses the above problem at the circuit level by electricallycoupling the ultrasonic receiver 404 with an attenuator circuit 408 onlyduring the blind zone time period so as to attenuate or removesubstantially all of the reverberation signals while allowing most, ifnot all, of the echo signals to pass through. Because the attenuation ofreceived signals is implemented at the circuit level, the cost increaseis minimal compared with the cost mechanical suppression ofreverberation discussed above.

In an embodiment, the ultrasonic receiver 404 is connected to a switch406 which is controllable by a switch control signal 420 provided by thecontroller 412. The switch control signal 420 can cause the switch 406to electrically couple the ultrasonic receiver 404 and the attenuatorcircuit 408 during the blind zone time period so as to attenuatereceived signals. The switch control signal 420 can also cause theswitch 406 to electrically decouple the ultrasonic receiver 404 and theattenuator circuit 408 so that the received signals are not attenuatedoutside the blind zone time period. In some embodiments, the decision tocouple or decouple the attenuator circuit 408 is based on a value of atimer (not shown). For example, the timer can be started when thetransmitter circuit stops driving the ultrasonic transmitter to transmitultrasonic signals. As long as the accumulated timer value does notexceed the blind zone time period, the switch 406 can remain in a statewhere the attenuator circuit 408 is selected. However, when the timervalue reaches or exceeds the blind zone time period, the switch controlsignal 420 causes the switch 406 to decouple from the attenuatorcircuit.

In some embodiments, the switch 406 can include a single-pole,double-throw (SPDT) switch or may include an arbitrary number of polesand/or throws. In other embodiment, switch can include a multiplexer(mux) demultiplexer (demux). The switch 406 can also include anelectronic switch such as a power metal-oxide-semiconductor field-effecttransistor (MOSFET), solid state relay, power transistor, insulated gatebipolar transistor (IGBT) or the like.

In various embodiments, the attenuator circuit 408 can include one ormore passive components forming voltage divider networks to reduce thepower of an electrical signal. For example, the attenuator circuit 408can include a diode and a capacitor or a resister and a capacitor. Thecomponents of the attenuator circuit may be arranged in accordance withany arrangement such as the Π-type or the T-type.

In various embodiments, the parameters of the attenuator circuit 408 maybe configurable to accommodate different circumstances in order toreduce or eliminate reverberation signals without eliminating echosignals. The parameters may be adjusted based on actual and/or previousmeasurement of reverberation signals and/or echo signals. For example,based on the amplitude of the actual reverberation signals and/or echosignals (e.g., as measured by an oscilloscope), parameters of passivecomponents of the attenuator circuit may be selected to achieve thedesired amount of attenuation such as discussed in connection with FIG.3. For example, the capacitance of a capacitor or resistance of aresistor can be selected to increase or decrease the overall amount ofattenuation such that it is sufficient to bring the amplitude ofreverberation signals below the triggering value and/or to close tozero.

In various embodiments, the characteristics (e.g., amplitude) associatedwith the actually measured reverberation signals and/or echo signals maybe determined by a variety of factors such as parameters or propertiesof the ultrasonic transmitter/receiver, installation position or methodof the ultrasonic transmitter/receiver (e.g., distance between thetransmitter probe and the receiver probe, whether mechanical vibrationreduction such as padding is in place, etc.), propagation medium,objects in the surrounding environment, and the like. For example,installed using similar methods, different ultrasonic probes may producedifferent reverberation and/or echo signals. Even the same ultrasonicprobes may produce different reverberation and/or echo signals wheninstalled differently.

According to another aspect of the present invention, methods andsystems are provided for dynamically adjusting gains associated theamplification of the echo signals to improve the accuracy and/or rangeof proximity measurement. Existing ultrasonic sensors sometimes includefixed-gain amplifiers, wherein the amount of gain is determined by thegain required to reach the maximum measuring distance. Under certaincircumstances, such a fixed-gain control approach can lead to inaccuratemeasurement results. In particular, in a crowded environment, theobjects closer than the maximum measuring distance can cause falsetriggering of the comparator, leading to inaccurate measurement. Forexample, during a proximity measurement against the ground, if the thereis a box on the ground that is within the transmission range of thetransmitter probe, then the echo from the box can reach the receiverprobe first due to over amplification caused by the fixed gain based onthe maximum measuring distance. In contrast, using the adjustable gaincontrol approach as described by the present invention, the gain valueis provided based on the measuring distance. Thus, a smaller gain isprovided for a shorter measuring distance, thereby avoidingover-amplification of the echo from close-range objects. As such, themeasurement accuracy of ultrasonic sensing systems is improved by thepresent invention.

In an illustrative embodiment, the ultrasonic sensing system 400includes a gain-adjustable amplifier 410 that is configured to amplifyreceived signals according to an adjustable gain control (AGC) signal418 provided dynamically by the controller 412. In an embodiment, thegain-adjustable amplifier 410 can be electrically coupled to theultrasonic receiver 404 via the switch 406. During the blind zone timeperiod, the gain-adjustable amplifier 410 can be connected in serieswith the attenuator circuit 408 so as to amplify the signals that havebeen attenuated by the attenuator circuit 408. Such post-attenuationamplification may be necessary to bring the attenuated echo signalsabove the triggering value in order to trigger proximity measurementprocessing. Beyond the blind zone time period, the gain-adjustableamplifier 410 can be used to directly amplify received signals bypassingthe attenuator circuit 408 (e.g., via the switch 406). Suchamplification of echo signals received outside the blind zone timeperiod can be used to compensate for the attenuation caused by thepropagation medium (e.g., air, water) increasing the range and accuracyof the proximity measurement.

In some embodiments, the gain provided by the gain-adjustable amplifier410 is dynamically adjusted based on the measuring distance. Once theultrasonic signals are transmitted, the measuring distance of theultrasonic sensing system increases as transmitted signal is propagatedfurther away. The farther the measuring distance, the more attenuatedthe echo signal is, due to the attenuation caused by the propagationmedium. Hence, more gain generally needs to be provided for the receivedsignals to compensate for the increasing attenuation as the measuringdistance increases over time. In an embodiment, the gain provided by thegain-adjustable amplifier 410 is dynamically adjusted to graduallyincrease (according to the AGC signal 418) as the measuring distanceincreases. The adjusted gain may be the same or more than apreviously-provided gain.

In some cases, the exact attenuation characteristics of the ultrasonicsignals may vary depending on the propagation media (e.g., air, water),transmission frequency, transmitter/receiver properties, installationmethods, and other factors. As such, the AGC signal 418 and hence thegain provided by gain-adjustable amplifier 410 can be provided based atleast in part on empirical measurement of the actual gains required toelevate a received echo signal to reach the triggering value ordetectable level (e.g., sufficient to trigger an interrupt by acomparator) at varying measuring distances. Alternatively, the gain canbe automatically adjusted based on the strength of the received signal.For example, the gain may be proportional to the strength of the receivesignal, for example, in a linear or exponential fashion.

FIG. 5 illustrates some exemplary AGC gain values (AGC values)associated with various measuring distances or measuring ranges, inaccordance with an embodiment. For a given measuring distance or range,the corresponding AGC gain is required to amplify the echo signalsreceived from that measuring distance or range to a detectable level(e.g., exceeding the triggering value defined by a comparator). Thetable on the left side of FIG. 5 shows the measuring ranges (“Range”) incentimeters (cm) in the left column and the corresponding AGC value(“POT AGC Value”) in logarithmic decibel (dB) in the right column. TheAGC value can be derived based on an input echo signal and an outputsignal as amplified by a gain-adjustable amplifier and can indicate thedegree the input signal is amplified. In an embodiment, the AGC valuesmay be measured by a potentiometer or other measuring instruments. Thus,the data shown in FIG.5 illustrates the correlation between AGC valueand the measuring distance. The chart on the left side of FIG. 5illustrates the same data. As shown by the table and the chart of FIG.5, the AGC value generally increases as the measuring distanceincreases. In some cases, the AGC value remains the same for two or moreconsecutive measuring ranges. In addition to the measuring distance, AGCvalues may also vary based on the properties of the transmitter/receiverprobes, installation methods, propagation medium and other factors.

To provide suitable AGC values for a particular ultrasonic sensingsystem in a particular environment, a test measurement may be performedto measure and/or calculate the AGC values (such as those illustrated inFIG. 5) prior to using the ultrasonic sensing system. During the testmeasurement, the echo signals for varying measuring distances can beanalyzed (e.g., using an oscillator) to determine the amplitude of theecho signals. For example, the measuring distances can be incremented atfixed intervals (e.g., 10 cm). Based on the amplitude of the receivedecho signals, the AGC value for the amplifier can be adjusted so as tobring the echo signals to above the triggering value (e.g., thethreshold value to trigger a comparator). During the actual proximitymeasurement, the AGC values derived from such test measurements can beused by the controller of the ultrasonic sensing system to provide gaincontrol signals to the gain-adjustable amplifier so as to attain thedesired amount of gain. Given that the change in measuring distance isproportional to the time that has elapsed since the start of thepropagation due to constant speed of propagation of sound, the measuringdistances shown in the table and chart of FIG. 5 can be converted to theamount of time that has elapsed since the start of the transmission ofultrasonic signals. In some embodiments, lookup tables or similar datastructures can be created and used for AGC values for particular sensorsand/or conditions. Based on such a lookup table, a time-based gaincontrol method can be provided to proximate the distance-based gaincontrol illustrated in FIG. 5.

FIG. 6 illustrates an exemplary process 600 for implementing atime-based gain control as described herein, in accordance with anembodiment. In particular, the process 600 can be used to providedynamically adjusted gain control to a gain-adjustable amplifier tocompensate for varying attenuation of input signals. For example, theamount of gain can be adjusted (e.g., incremented or kept the same) astime increases based on the previously measured and/or calculated AGCdata. In an embodiment, aspects of the process 600 can be implemented bythe controller 412 of FIG. 4.

In an embodiment, the process 600 includes waiting 602 for predeterminedinterrupts. Such predetermined interrupts can indicate the occurrence ofpredetermined events that require handling, for example, by an interrupthandler or an Interrupt Service Routine (ISR). For example, such aninterrupt may be triggered by a comparator when the input signal isgreater than a predetermined triggering value. As another example, aninterrupt can be triggered when an output of an analog-to-digitalconverter (ADC) has reached a predetermined threshold value.

At block 604, it is determined whether an interrupt has occurred. If so,the process 600 includes processing 602 the interrupt, for example, byexecuting the ISR to calculate the proximity to an object. If not, theprocess 600 includes returning to the waiting block 602.

In an embodiment, the process 600 includes determining 606 whether apredetermined increment of time At has elapsed. If so, the AGC gainvalue is adjusted 608. Otherwise, the process 600 includes returned tothe waiting block 602. Thus, the AGC gain value is adjusted at fixedtime intervals. The time interval At can be configurable to anyarbitrary time interval. Alternatively, the AGC value can be adjusted atvarying time intervals or in response to predetermined events. In someembodiments, adjusting the AGC gain value can include looking up theempirical AGC data such as illustrated in FIG. 5 or variations thereofto determine a suitable AGC value corresponding to the current measuringdistance, or equivalently, the current elapsed time. For example, basedon the current timer value, it may be determined that the currentmeasuring distance is in the 70-80 cm range (based on the propagationspeed of the ultrasonic signal) and the corresponding AGC value is 9 dBaccording to the table in FIG. 5. Additionally or alternatively, the AGCvalue can be adjusted based on other factors such as an output from acomparator and/or analog-to-digital converter (ADC), various parametersassociated with the ultrasonic sensing system, and the like. Based onsome or all of these factors, a suitable control signal may be generatedby the AGC value and provided to a gain-adjustable amplifier to attainthe desirable gain amount. In some embodiments, process 600 is continueduntil the time period corresponding to the maximum measuring distanceexpires. Such maximum measuring distance can configurable.

According to another aspect of the present invention, methods andsystems are provided for using the analog-to-digital converter (ADC) inconjunction with a comparator to improve the precision and accuracy ofproximity measurement. For example, the ultrasonic sensing system 400 inFIG. 4 includes a comparator 414 and an ADC 416, each connected to thegain-adjustable amplifier 410. The comparator 414 can be configured tocompare an input signal from the gain-adjustable amplifier 410 with apredetermined triggering value (e.g., voltage) to provide an indicationof whether the input signal is greater than the predetermined triggeringvalue. For example, the comparator 414 may be configured to output a “1”if the input signal is greater than the triggering value and a “0”otherwise. In some embodiments, an output of the comparator (e.g., a“1”) can trigger an interrupt such as discussed in FIG. 6, causing theexecution of an ISR. The ADC 416 can be configured to convert an analogsignal to a digital signal that represents the amplitude (e.g., voltage)of the signal. In some cases, the output of the ADC can be used totrigger an interrupt. For example, such an interrupt can be triggeredwhen the output of the ADC exceeds a predetermined threshold value. Insome embodiments, comparator 414 and/or the ADC 416 can be included as apart of or integrated with the controller 412 such as illustrated inFIG. 4. Alternatively, the comparator 414 and/or the ADC 416 can beexternal to the controller 412.

In some embodiments, the comparator 414 and the ADC 416 can be used inconjunction to improve the accuracy and precision of the measurement ofthe echo signals. In particular, the comparator 414 can be used totrigger proximity measurement and measurements from the ADC 416 can beused to determine, within a predetermined period of time, a point intime when the relative peak amplitude is received. This point in timecan then be used in the calculation of the distance to the object fromwhich the echo signal is received. By pinpointing the time of the peakamplitude, accuracy of the proximity measurement is improved.

Generally, proximity to an object is calculated based on the timeinterval between the transmission and the receipt of an ultrasonicsignal as reflected by the object. The transmission of the ultrasonicsignal is typically at the time of transmission of the transmittingwave's peak. If the time of the receipt of the ultrasonic signal is setat the time the comparator is triggered by the reflected wave, themeasurement is less than accurate because there is a period of timebetween when a comparator is triggered by the reflected wave (e.g.,below the peak amplitude) and when the peak amplitude is reached. Withan ADC, it would be relatively easy to detect peak value of thereflected wave and when the peak value is detected. The time when thepeak value is detected can then be used to calculate the distance to theobject, thereby improving the accuracy of the measurement.

FIG. 7 illustrates an exemplary process 700 for determining theoccurrence of peak amplitude, in accordance with an embodiment. Theprocess 700 can be implemented, for example, by software, hardware, or acombination thereof embedded in the controller 412 or elsewhere.

In some embodiments, the process 700 includes determining that the ADCis ready for measurement. In some cases, the ADC is activated formeasurement after the comparator is triggered by a received signal.Additionally, an ADC can be configured to take measurement only atcertain time intervals. Such time intervals may be configurable by amanufacturer of the ADC, a user of the ADC (e.g., developer, end user,etc.) or the like.

When the ADC is ready for measurement, the current ADC value, ADC., isobtained 704 using the ADC. The ADC value represents the digitalizedamplitude value of the input signal to the ADC. The current ADC value,ADC_(curr), can be compared with a previously obtained ADC value,ADC_(old), to determine 706 whether ADC_(curr)>ADC_(old). In a typicalembodiment, ADC_(old) is the ADC value in the immediately precedingmeasurement. In some embodiments, ADC_(old) is set to 0 at the first ADCmeasurement and/or after each detection of a peak amplitude (e.g., at orafter block 708).

If it is determined that the current ADC value is greater than thepreviously obtained ADC value, it likely means that the peak amplitudehas not arrived yet. Therefore, the process 700 proceeds to block 702 tostart the next round of measurement. If, however, the previouslyobtained ADC value is equal to or greater than the current ADC value,then it means that the peak has been is reached. The current timer valuet_(peak) is recorded 708. In some embodiments, the timer is started atthe transmission of the ultrasonic signal. As such, t_(peak) representsthe time interval between the transmission and the receiving of the peakof the ultrasonic signal as reflected by an object.

In some embodiments, the process 700 may be used to detect more than oneobject within the measurement range of an ultrasonic sensor. As such,there can be more than one t_(peak)'s, each associated with a differentobject. To implement detection of multiple peak amplitude values, theprocess 700 can include iterating the above process to derive multiplet_(peak)'s as long as the measurement time is not over. Before the startof the iteration of measurement, ADC_(old) may be reset to 0. Themeasurement time typically refers to the time period required to measurea maximum distance from a proximity sensing system implementing theprocess 700. The measurement time can be determined by thecharacteristics of the proximity sensing system, the surroundingenvironment, and/or configurable by a manufacturer, a user, a customer,or the like.

In some embodiments, the process 700 includes determining 710 whetherthe measurement time is over. If measurement time is over, then the oneor more t_(peak) values are returned 712. Otherwise, if the measurementtime is not over, the process 700 includes looping back to block 702 tostart another iteration of determining when peak amplitude value occurs.

Referring back to FIG. 4, in some embodiments, the comparator 414 and/orADC 416 can be used to control the gain-adjustable amplifier 410 and/orthe switch 406 discussed above. For example, the AGC signal 418 and/orthe switch control signal 420 may be generated based on an output fromthe comparator 414 and/or ADC 416.

In some embodiments, the controller 412 can include a microcontrollerunit (MCU) on a single integrated circuit board. In some otherembodiments, the controller 412 can include a distributed computingsystem. The controller 412 can include a processing unit 424, a memory426 and input/output peripherals (not shown). The processing unit 424can include one or more processors, such as a programmable processor(e.g., a central processing unit (CPU)). The processing unit 424 can beoperatively coupled to the memory 426. The memory 426 can include one ormore units of transitory and/or non-transitory storage media configuredto store data, and/or logic, code, and/or program instructionsexecutable by the processing unit 424 for performing one or moreroutines or functions. For example, the memory units may include randomaccess memory (RAM), read-only memory (ROM), erasable programmableread-only memory (PROM), electrically erasable programmable read-onlymemory (EEPROM), and the like. The memory units of memory 426 can storedata such as the AGC value data or variations thereof discussed in FIG.5, input/output data including such as data from the comparator, ADC,timer, sensor, or the like, processing results from the processing unit424, and the like. In addition, the memory units of the memory 426 canstore operating parameters and/or logic, code and/or programinstructions executable by the processing unit 424 to perform anysuitable embodiment of the methods described herein. For example, theprocessing unit 424 can be configured to execute instructions causingone or more processors of the processing unit 424 to provide switchcontrol signal 420 to the switch 406 in order to implement thetime-based attenuation as discussed in FIG. 3. In addition, theprocessing unit 424 can be configured to execute instructions causingone or more processors of the processing unit 424 to provide AGC controlsignal to the gain-adjustable amplifier 410 so as to implement thedistance-based amplification of received signals such as discussed inconnection with FIG. 6. Furthermore, the processing unit 424 can beconfigured to execute instructions causing one or more processors of theprocessing unit 424 to determine the occurrence (including the timing)of peak amplitude based on the input from the comparator and the ADCsuch as discussed above. Although FIG. 4 depicts a single processingunit 424 and a single memory 426, one of skill in the art wouldappreciate that this is not intended to be limiting, and that the system400 can include a plurality of processing units and/or memory units ofthe memory.

In some embodiments, the controller 412 can also include a plurality ofinput/output peripherals (now shown). For example, the controller 412can include one or more discrete input/out bits, allowing control and/ordetection of the logic state of an individual package pin. Alternativelyor additionally, the controller 412 can include one or more serialinput/output such as serial ports (e.g., universal asynchronousreceiver/transmitters (UARTs)). The controller 412 can also include oneor more serial communication interfaces such as Inter-Integrated Circuit(I²C), Serial Peripheral Interface (SPI) bus, Controller Area Network(CAN) bus, or the like, for system interconnect. In some cases, thecontroller 412 can also include one or more peripherals such as timers,event counters, pulse-width modulation (PWM) generators, clock generator(e.g., an oscillator for quartz timing crystal, resonator or RCcircuit), and the like. In some cases, the controller 412 can alsoinclude one or more digital-to-analog converters, in-circuit programmingand/or debugging support, USB and Ethernet support, and the like.

While the methods and systems of the present invention are described inthe context of ultrasonic sensing systems, it is appreciated thataspects of the methods and systems of the present invention can also beapplicable to a wide variety of proximity sensing systems using radar,sonar, lidar, or other sensing technologies.

In some embodiments, the methods and systems described herein can beused by a movable object to provide information with respect the movableobject and/or the surrounding environment such as proximity to targetobjects (e.g., potential obstacles), location of geographical features,location of manmade structures, and the like. Such information may beused by the movable object to sense spatial disposition, velocity,and/or acceleration of the movable object (e.g., with respect to up tothree degrees of translation and up to three degrees of rotation).Additionally, the information can aid the operations of the movableobject including but not limited to path planning, autonomous navigationof the movable object along a predetermined flight path, obstacleavoidance, and the like.

The movable object (e.g., a UAV) may include one or more sensors thatmay sense the spatial disposition, velocity, and/or acceleration of themovable object (e.g., with respect to up to three degrees of translationand up to three degrees of rotation). The one or more sensors caninclude global positioning system (GPS) sensors, motion sensors,inertial sensors, proximity sensors (e.g., ultrasonic sensor and/orlidar sensor), image sensors, and the like. In some embodiments, theproximity sensor can be rotated (e.g., rotated 360°) to obtain distanceand position information for a plurality of objects surrounding themovable object. The distance and position information for thesurrounding objects can be analyzed to determine the spatial dispositionand/or motion of the movable object and/or aid in the navigation of themovable object.

The movable object may also include a controller for controlling theoperations of the movable object and/or the components thereof. Themovable object can also be controlled remotely by a user or controlledlocally by an occupant within or on the movable object. In someembodiments, the movable object is an unmanned movable object, such asan unmanned aerial vehicle (UAV). An unmanned movable object, such as aUAV, may not have an occupant onboard the movable object. The movableobject can be controlled by a human or an autonomous control system(e.g., a computer control system), or any suitable combination thereof.The movable object can be an autonomous or semi-autonomous robot, suchas a robot configured with an artificial intelligence.

In some embodiments, aspects of the methods and systems described hereincan be implemented by the movable object, a remote control device, or acombination thereof. For example, the controller 412 of the proximitysensing system 400 can be implemented by the controller onboard themovable object that is also capable of controlling the operations of themovable object or a controller off board the movable object such as in aremote control device or base station terminal. For example, the controlsignals for the switch and/or the gain-adjustable amplifier in FIG. 4can be provided by the controller of the movable object and/or theremote control device. As another example, the proximity measurement andcalculation can be performed by the controller of the movable object, aremote control device, a base station or some third-party device. Invarious embodiments, the controller of the proximity sensing system maybe separate from or integrated with the controller of the movableobject. In some embodiments, the same remote control device may beoperable to control the movable object and the proximity sensing system.In other embodiments, separate remote control devices may be used tocontrol the movable object and the proximity sensing system. In someembodiments, data provided by the proximity sensing systems describedherein may be used alone or in conjunction with data from other sensorsor sensing systems onboard and/or off board the movable object such asGPS sensors, motion sensors, inertial sensors, proximity sensors, imagesensors, and the like, to provide positional, attitude and/or otherstate information about the movable object and/or the environmentsurrounding the movable object.

In various embodiments, the movable object can be configured to movewithin any suitable environment, such as in air (e.g., a fixed-wingaircraft, a rotary-wing aircraft, or an aircraft having neither fixedwings nor rotary wings), in water (e.g., a ship or a submarine), onground (e.g., a motor vehicle, such as a car, truck, bus, van,motorcycle; a movable structure or frame such as a stick, fishing pole;or a train), under the ground (e.g., a subway), in space (e.g., a spaceplane, a satellite, or a probe), or any combination of theseenvironments. The movable object can be mounted on a living subject,such as a human or an animal. Suitable animals can include avines,canines, felines, equines, bovines, ovines, porcines, delphines,rodents, or insects.

The movable object may be capable of moving freely within theenvironment with respect to six degrees of freedom (e.g., three degreesof freedom in translation and three degrees of freedom in rotation).Alternatively, the movement of the movable object can be constrainedwith respect to one or more degrees of freedom, such as by apredetermined path, track, or orientation. The movement can be actuatedby any suitable actuation mechanism, such as an engine or a motor. Theactuation mechanism of the movable object can be powered by any suitableenergy source, such as electrical energy, magnetic energy, solar energy,wind energy, gravitational energy, chemical energy, nuclear energy, orany suitable combination thereof.

In some instances, the movable object can be a manned or unmannedvehicle. Suitable vehicles may include water vehicles, aerial vehicles,space vehicles, or ground vehicles. For example, aerial vehicles may befixed-wing aircraft (e.g., airplane, gliders), rotary-wing aircraft(e.g., helicopters, rotorcraft), aircraft having both fixed wings androtary wings, or aircraft having neither (e.g., blimps, hot airballoons). A vehicle can be self-propelled, such as self-propelledthrough the air, on or in water, in space, or on or under the ground. Aself-propelled vehicle can utilize a propulsion system, such as apropulsion system including one or more engines, motors, wheels, axles,magnets, rotors, propellers, blades, nozzles, or any suitablecombination thereof. In some instances, the propulsion system can beused to enable the movable object to take off from a surface, land on asurface, maintain its current position and/or orientation (e.g., hover),change orientation, and/or change position.

For example, the propulsion system can include one or more rotors. Arotor can include one or more blades (e.g., one, two, three, four, ormore blades) affixed to a central shaft. The blades can be disposedsymmetrically or asymmetrically about the central shaft. The blades canbe turned by rotation of the central shaft, which can be driven by asuitable motor or engine. The blades can be configured to spin in aclockwise rotation and/or a counterclockwise rotation. The rotor can bea horizontal rotor (which may refer to a rotor having a horizontal planeof rotation), a vertically oriented rotor (which may refer to a rotorhaving a vertical plane of rotation), or a rotor tilted at anintermediate angle between the horizontal and vertical positions. Insome embodiments, horizontally oriented rotors may spin and provide liftto the movable object. Vertically oriented rotors may spin and providethrust to the movable object. Rotors oriented an intermediate anglebetween the horizontal and vertical positions may spin and provide bothlift and thrust to the movable object. One or more rotors may be used toprovide a torque counteracting a torque produced by the spinning ofanother rotor.

The movable object can have any suitable size and/or dimensions. In someembodiments, the movable object may be of a size and/or dimensions tohave a human occupant within or on the vehicle. Alternatively, themovable object may be of size and/or dimensions smaller than thatcapable of having a human occupant within or on the vehicle. The movableobject may be of a size and/or dimensions suitable for being lifted orcarried by a human. Alternatively, the movable object may be larger thana size and/or dimensions suitable for being lifted or carried by ahuman. In some instances, the movable object may have a maximumdimension (e.g., length, width, height, diameter, diagonal) of less thanor equal to about: 2 cm, 5 cm, 10 cm, 50 cm, 1 m, 2 m, 5 m, or 10 m. Themaximum dimension may be greater than or equal to about: 2 cm, 5 cm, 10cm, 50 cm, 1 m, 2 m, 5 m, or 10 m. For example, the distance betweenshafts of opposite rotors of the movable object may be less than orequal to about: 2 cm, 5 cm, 10 cm, 50 cm, 1 m, 2 m, 5 m, or 10 m.Alternatively, the distance between shafts of opposite rotors may begreater than or equal to about: 2 cm, 5 cm, 10 cm, 50 cm, 1 m, 2 m, 5 m,or 10 m.

In some embodiments, the movable object may have a volume of less than100 cm×100 cm×100 cm, less than 50 cm×50 cm×30 cm, or less than 5 cm×5cm×3 cm. The total volume of the movable object may be less than orequal to about: 1 cm³, 2 cm³, 5 cm³, 10 cm³, 20 cm³, 30 cm³, 40 cm³, 50cm³, 60 cm³, 70 cm³, 80 cm³, 90 cm³, 100 cm³, 150 cm³, 200 cm³, 300 cm³,500 cm³, 750 cm³, 1000 cm³, 5000 cm³, 10,000 cm³, 100,000 cm³, 1 m³, or10 m³. Conversely, the total volume of the movable object may be greaterthan or equal to about: 1 cm³, 2 cm³, 5 cm³, 10 cm³, 20 cm³, 30 cm³, 40cm³, 50 cm³, 60 cm³, 70 cm³, 80 cm³, 90 cm³, 100 cm³, 150 cm³, 200 cm³,300 cm³, 500 cm³, 750 cm³, 1000 cm³, 5000 cm³, 10,000 cm³, 100,000 cm³,1 m³, or 10 m³.

In some embodiments, the movable object may have a footprint (which mayrefer to the lateral cross-sectional area encompassed by the movableobject) less than or equal to about: 32,000 cm², 20,000 cm², 10,000 cm²,1,000 cm², 500 cm², 100 cm², 50 cm², 10 cm², or 5 cm². Conversely, thefootprint may be greater than or equal to about: 32,000 cm², 20,000 cm²,10,000 cm², 1,000 cm², 500 cm², 100 cm², 50 cm², 10 cm², or 5 cm².

In some instances, the movable object may weigh no more than 1000 kg.The weight of the movable object may be less than or equal to about:1000 kg, 750 kg, 500 kg, 200 kg, 150 kg, 100 kg, 80 kg, 70 kg, 60 kg, 50kg, 45 kg, 40 kg, 35 kg, 30 kg, 25 kg, 20 kg, 15 kg, 12 kg, 10 kg, 9 kg,8 kg, 7 kg, 6 kg, 5 kg, 4 kg, 3 kg, 2 kg, 1 kg, 0.5 kg, 0.1 kg, 0.05 kg,or 0.01 kg. Conversely, the weight may be greater than or equal toabout: 1000 kg, 750 kg, 500 kg, 200 kg, 150 kg, 100 kg, 80 kg, 70 kg, 60kg, 50 kg, 45 kg, 40 kg, 35 kg, 30 kg, 25 kg, 20 kg, 15 kg, 12 kg, 10kg, 9 kg, 8 kg, 7 kg, 6 kg, 5 kg, 4 kg, 3 kg, 2 kg, 1 kg, 0.5 kg, 0.1kg, 0.05 kg, or 0.01 kg.

In some embodiments, a movable object may be small relative to a loadcarried by the movable object. The load may include a payload and/or acarrier, as described in further detail below. In some examples, a ratioof a movable object weight to a load weight may be greater than, lessthan, or equal to about 1:1. In some instances, a ratio of a movableobject weight to a load weight may be greater than, less than, or equalto about 1:1. Optionally, a ratio of a carrier weight to a load weightmay be greater than, less than, or equal to about 1:1. When desired, theratio of an movable object weight to a load weight may be less than orequal to: 1:2, 1:3, 1:4, 1:5, 1:10, or even less. Conversely, the ratioof a movable object weight to a load weight can also be greater than orequal to: 2:1, 3:1, 4:1, 5:1, 10:1, or even greater.

In some embodiments, the movable object may have low energy consumption.For example, the movable object may use less than about: 5 W/h, 4 W/h, 3W/h, 2 W/h, 1 W/h, or less. In some instances, a carrier of the movableobject may have low energy consumption. For example, the carrier may useless than about: 5 W/h, 4 W/h, 3 W/h, 2 W/h, 1 W/h, or less. Optionally,a payload of the movable object may have low energy consumption, such asless than about: 5 W/h, 4 W/h, 3 W/h, 2 W/h, 1 W/h, or less.

While preferred embodiments of the present invention have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. Numerousvariations, changes, and substitutions will now occur to those skilledin the art without departing from the invention. It should be understoodthat various alternatives to the embodiments of the invention describedherein may be employed in practicing the invention. It is intended thatthe following claims define the scope of the invention and that methodsand structures within the scope of these claims and their equivalents becovered thereby.

1.-30. (canceled)
 31. An ultrasonic sensing system, comprising: anattenuator circuit connectable to an ultrasonic receiver via a switchand configured to attenuate ultrasonic signals received by theultrasonic receiver, wherein the ultrasonic signals comprise areverberation signal and an echo signal; and a controller configured tocontrol the switch so as to electrically couple the attenuator circuitwith the ultrasonic receiver during a predetermined period of time aftera transmission of an ultrasonic signal and electrically decouple theattenuator circuit from the ultrasonic receiver prior to and after thepredetermined period of time.
 32. The system of claim 31, wherein thepredetermined period of time corresponds to a blind zone time period forthe ultrasonic sensing system.
 33. The system of claim 31, wherein theattenuator circuit is configured to provide an amount of attenuationselected based at least in part on a previously measured amplitude of areverberation signal or an echo signal.
 34. The system of claim 31,further comprising a gain-adjustable amplifier operably coupled to thecontroller and configured to amplify the echo signal.
 35. The system ofclaim 34, wherein the controller is further configured to vary a gain ofthe gain-adjustable amplifier based at least in part on a value of atimer that corresponds to a measuring distance.
 36. The system of claim34, wherein the controller is further configured to vary a gain of thegain-adjustable amplifier based at least in part on previously measureddata.
 37. The system of claim 34, wherein the controller is furtherconfigured to control the switch to electrically couple thegain-adjustable amplifier with the ultrasonic receiver after thepredetermined period of time has elapsed.
 38. The system of claim 34,further comprising a comparator coupled to the gain-adjustable amplifierand configured to compare an output of the gain-adjustable amplifierwith a predetermined threshold value.
 39. The system of claim 38,further comprising an analog-to-digital converter (ADC) coupled to thegain-adjustable amplifier and configured to convert the output of thegain-adjustable amplifier to a digital value.
 40. The system of claim39, wherein the controller is further configured to determine anoccurrence of a peak amplitude of a received ultrasonic signal using thecomparator and the ADC.
 41. A method for operating an ultrasonic sensingsystem, comprising: determining whether an ultrasonic signal detected byan ultrasonic receiver occurs within a predetermined period of timeafter termination of a transmission of an ultrasonic signal, wherein thedetected ultrasonic signal comprises a reverberation signal and an echosignal; in response to a determination that the detected ultrasonicsignal occurs within the predetermined period of time, electricallycoupling the ultrasonic receiver with an attenuator circuit so as toattenuate the reverberation signal; and electrically decoupling theultrasonic receiver from the attenuator circuit when the predeterminedperiod of time has elapsed.
 42. The method of claim 41, wherein thepredetermined period of time corresponds to a blind zone time period forthe ultrasonic sensing system.
 43. The method of claim 41, wherein theattenuator circuit is configured to provide an amount of attenuationselected based at least in part on a previously measured amplitude of areverberation signal or an echo signal.
 44. The method of claim 41,further comprising amplifying the echo signal with aid of again-adjustable amplifier.
 45. The method of claim 44, furthercomprising varying a gain of the gain-adjustable amplifier based atleast in part on a value of a timer that corresponds to a measuringdistance.
 46. The method of claim 44, further comprising varying a gainof the gain-adjustable amplifier based at least in part on previouslymeasured data.
 47. The method of claim 44, further comprisingelectrically coupling the gain-adjustable amplifier with the ultrasonicreceiver after the predetermined period of time has elapsed.
 48. Themethod of claim 44, further comprising comparing an output of thegain-adjustable amplifier with a predetermined threshold value with aidof a comparator.
 49. The method of claim 48, further comprisingconverting the output of the gain-adjustable amplifier to a digitalvalue with aid of an analog-to-digital converter (ADC).
 50. The methodof claim 49, further comprising determining an occurrence of a peakamplitude of a received ultrasonic signal using the comparator and theADC.